Radiation curable compositions for coating and imaging processes and method of use

Abstract

This invention relates to a liquid radiation curable composition useful for coating and imaging which comprises (1) an acrylic or methacrylic terminated, urethane containing polyene, (2) a non-water soluble vinyl monomer diluent, preferably an acrylate or methacrylate monomer diluent, (3) a polythiol containing at least two thiol groups per molecule and (4) a photoinitiator. The composition on exposure to radiation, e.g., a U.V. light source, cures to a solid polythioether.

We claim: 
     
       1. A liquid radiation curable composition comprising (1) 10 to 80% by weight of an acrylic or methacrylic terminated, urethane containing polyene,   (2) 5 to 60% by weight of a non-water soluble vinyl monomer diluent,   (3) 0.1 to 35% by weight of a polythiol and   (4) 0.01 to 10% by weight of a photoinitiator, which forms a solid cured polythioether on exposure to actinic or high energy ionizing radiation.     
     
     
       2. The liquid radiation curable composition according to claim 1 wherein said polyene is prepared by reacting diisocyanate monomer with an ethylenically unsaturated alcohol in an amount such that one stoichiometric equivalent of diisocyanate groups remain in the reaction product and thereafter reacting said free isocyanate groups with the stoichiometric equivalent of the hydroxyl groups in a polyhydric alcohol. 
     
     
       3. The liquid radiation curable composition according to claim 2 wherein the diisocyanate is toluene diisocyanate, the ethylenically unsaturated alcohol is hydroxy propyl methacrylate and the polyhydric alcohol is polypropylene glycol having a molecular weight in the range 1,000 to 2,000. 
     
     
       4. The process of forming a printing plate which comprises exposing to actinic radiation projected through an image-bearing transparency selected portions of a radiation curable composition comprising (1) 10 to 80% by weight of an acrylic or methacrylic terminated, urethane containing polyene,   (2) 5 to 60% by weight of a non-water soluble vinyl monomer diluent,   (3) 0.1 to 35% by weight of a polythiol and   (4) 0.01 to 10% by weight of a photoinitiator for a time sufficient to insolubilize the radiation curable composition in the exposed portions and thereafter removing the unexposed radiation curable composition.   
     
     
       5. The process of claim 4 wherein the radiation curable composition is adhered to a support layer during exposure to actinic radiation. 
     
     
       6. The process according to claim 4 wherein an airgap from about 0.1 to about 250 mils is maintained between the image-bearing transparency and the radiation curable composition during exposure to actinic radiation. 
     
     
       7. The process of forming a coating on a substrate which comprises applying to the surface of a substrate a layer of a composition comprising (1) 10 to 80% by weight of an acrylic or methacrylic terminated, urethane containing polyene,   (2) 5 to 60% by weight of a non-water soluble vinyl monomer diluent,   (3) 0.1 to 35% by weight of a polythiol and   (4) 0.01 to 10% by weight of a photoinitiator and thereafter exposing the layer to actinic radiation thereby curing said composition.   
     
     
       8. The process of forming a coating on a substrate which comprises applying to the surface of a substrate a layer of a composition comprising (1) 10 to 80% by weight of an acrylic or methacrylic terminated, urethane containing polyene,   (2) 5 to 60% by weight of a non-water soluble vinyl monomer diluent and   (3) 0.1 to 35% by weight of a polythiol and thereafter exposing the layer to high energy ionizing radiation thereby curing said composition.